According to a recent piece by Bill Simmons, the New Jersey Nets could have traded their top 3 protected draft pick to Boston for Paul Pierce before the trade deadline this year, but instead opted to trade it to Portland for Gerald Wallace.

The trade deadline passed with Rondo reinvested and Garnett reenergized.
You know who else stuck around? The second-leading scorer in Celtics
history, Paul Pierce, who stunk in February (16.4 PPG, 39.5% FG) and
inadvertently murdered his own trade value. Remember when New Jersey's
bid for Dwight Howard fell through, then they panicked and swapped a
top-three protected 2012 pick to Portland for Gerald Wallace, and
everyone said, "Wait a second, why would someone give up a top-three
protected pick for the third-best player on a sub-.500 team?" Not
reported at the time: New Jersey could have landed Pierce for that same
pick, only they chose Wallace because he was a full five years younger.3

Personally, I am really happy this didn't happen. The Celtics are finally clicking and getting back to Celtics basketball. The chemistry has been great, and Ubuntu has been restored. Everything happens (or doesn't happen) for a reason, right? Banner 18, here we come...